Inductive heating apparatus



INDUCTIVE HEATING APPARATUS Filed March a, 1968 Sheet of 2 Fig.1

In ventors Z-TQIEFHELM /Fs'/A/K zf/ywme Win 5 A ain-i129, 1969 INDUCTIVE HEATING APPARATUS Filed March 8, 1968 Fig. 2

In venture ff/zaA z/v zFV/VKE AI'mRNEYS F. R. REINKE ETAL 3,441,703

United States Patent Int. Cl. Hb 5/00, 9/02 U.S. Cl. 21910.69 4 Claims ABSTRACT OF THE DISCLOSURE Improved apparatus for inductively heating metal workpieces, comprising two rotatable spiders adapted to carry workpieces between centres consecutively 1nto several treating positions by an indexing mechanism; the improvement which comprises an automatic control mechanism for lifting and lowering the inductor from and to a heating position when a workpiece is indexed to a heating station, said control mechanism comprising a rocking lever adapted and arranged to raise and lower an inductor in response to rocking motions thereof derived from the interaction of a roller on an end thereof with a heart-shaped disc cam mounted on the drive shaft for the indexing mechanism.

This invention relates to apparatus for inductively hardening elongate workpieces of the kind in which the workpieces that are to be treated are held between centres on the ends of the arms of two spiders and are thus moved by predetermined automatically produced rotations of the spiders first to a heating station and then into a quench- I ing bath and/or into range of a sprayer for quenching.

It has previously been proposed to predetermine the timing and degree of rotation of the pair of spiders, by mounting on the common shaft of the spiders a slot cam cooperating with a roller which engages said slots and which is thus guided to move along a loop path generated by a crank and rocker linkage. While such mechanisms have been reasonably satisfactory in practice, a disadvantage which remains is the lack of a suitable mechanism for moving the inductor during the cycle of operations.

Since the inductor must be advanced into close proximity with the workpiece in order to provide a good inductive heating effect, it is necessary in apparatus of the kind hereinbefore described to lift the inductor before the heated workpieces can be removed or before the cold workpiece is indexed into a position beneath the inductor, and then to lower the same into the working position.

An object of the invention is to provide means whereby such movements of the inductor are also controlled automatically. With such automatic control it is necessary in order to prevent damage to the inductor being lowered when no workpiece is in position between the centres of the spiders, or if a mounted workpiece is not in its proper prescribed position, to provide means to prevent the inductor being lowered in such circumstances.

The invention consists of apparatus for inductively heating metal workpieces, comprising two spiders, a rotatable shaft on which the said spiders are fixedly mounted; holding centres for workpieces on each of the arms of the said two spiders whereby workpieces may be held between corresponding arms of the said spiders during rotation thereof; means for rotating the said spiders consecutively through predetermined angles whereby workpieces mounted on the arms of the said spiders are moved consecutively into several treating positions, the said 3,441,703 Patented Apr. 29, 1969 means comprising a slot cam fixedly mounted on the said shaft and cooperating with a roller whereby movement of the roller along a path describing a loop and generated by rotation of a drive shaft having a crank and a rocker linkage, imparts an indexing motion to the spider; the improvement which comprises an automatic control mechanism for lifting and lowering the inductor from and to a heating position when a workpiece is indexed to a heating station, said control mechanism com prising a rocking lever adapted and arranged to raise and lower an inductor in response to rocking motions thereof; a heart shaped disc cam mounted on the aforesaid drive shaft having a crank and rocker linkage; and a follower roller on the said rocking lever cooperating with the said heart-shaped disc cam, whereby the inductor moves to and from a heating position in response to rotation of the said heart-shaped disc cam; and arresting means for preventing movement of the inductor to a heating position in the absence of misalignment of the workpiece in an indexed heating station.

In a preferred embodiment of the invention the arresting means for cooperation with the rocking lever is a retainer pawl held in inoperative position against the thrust of a spring by an electromagnet, e.g., solenoid, the said electromagnet being associated with an electrical circuit controlled by a sensor or switch means adjacent to the position where the workpieces are mounted.

An embodiment of the invention is hereafter described and illlustrated in the accompanying drawings, of which:

FIGURE 1 is a schematic side elevation of an arrangement according to the invention, and

FIGURE 2 is a section on the line AB of FIGURE 1.

Referring to the drawings, FIGURE 1 shows only the upper ends of arms 1 of a pair of spiders which carry workpieces 2 between centres not shown. A slot cam 3 provided with slots 4, 5 and 6, is secured attached to a shaft common to the two spiders. Above the slot 4 a workpiece 2 is shown in position for heating by an inductor 7 which is attached to a lever arm 8. This lever arm together with a transformer 9 and possibly other parts of associated electrical equipment is rigidly mounted on a shaft 10, which shaft also rigidly carries a rocking lever 11. The free end of the rocking lever 11 carries a follower roller 12 which is adapted to roll on the profile of a heart-shaped disc cam 13.

The disc cam 13 together with a crank to which a link 14 is pivotably attached, is mounted on shaft 15. The shaft 15 is driven by a motor 16 through worm gearing not specially shown in the drawings. Rotation of the said crank is converted by the said link 14 and a rocker 17 into motion of a roller 18 along a loop indicated by a dash-dotted line 19.

The mechanism functions as follows: When the inductively heated workpiece has reached the required temperature, the heating periods being constant and controlled for instance by an adjustable timing relay, the supply of electrical power is cut off. The motor is simultaneously started to rotate the shaft 15 and the associated crank in the direction indicated by an arrow 20. When the shaft has turned through an angle of the point of contact of the profile of the disc cam with the follower roller 12 will have moved from a to 0. Owing to the increase in diameter of the cam shaft 13 during this movement, the rocking lever 11 will have been raised, and since the inductor 7 is rigidly connected to the rocking lever, the inductor will have been simultaneously lifted away from the workpiece. During the same period of time the roller 18 will have been moved along the slot 5 from a point a to a point b on the dash-dotted line 19, without however imparting rotary motion to the slot cam 3.

As the shaft 15 continues to rotates through a further ice angle of 180 the' follower roller 12 rolls on the profile of the disc cam 13 from c to b. During the whole of this period the inductor 7 remains in its raised position. However, the roller 18 is forced to move along the dashdotted line 19 from b to c and thereby causes the slot cam 3 to be indexed through an angle of 120. If a workpiece is thereby carried into position underneath the raised inductor, the point of contact of roller 12 with the disc cam 13 will move from b to its starting point a. As a consequence the inductor will be lowered over the workpiece. The roller 18 simultaneously travels along the slot games 0 to a without imparting further motion to the slot cam 3.

In the event of the absence of a workpiece between the centres the disc cam will still move from b and a. However, when this motion begins, a solenoid 21 show in FIGURE 2 is deenergized. Before the rocking lever 11 reaches its fully raised position, said corresponding approximately for example to point c on the cam disc 13, a retaining pawl 22 will have been advanced by the thrust of a spring 23 under the rocking lever released by the deenergizing of the said solenoid in response to sensing and circuit means not shown, thereby preventing the latter from descending again so that the inductor is kept in its raised position.

Apart from the obvious mechanical advantages, such as the protection afforded to the inductor against mechanical damage, the described mechanism and the manner in which it functions avoids unnecessary delay in the working cycle when no workpiece is mounted between two of the centres of the spider. As soon as a fresh workpiece is accepted by the spiders at the transfer station on the right the solenoid 21 is reenergised and the retaining pawl is Withdrawn.

What is claimed is:

1. Apparatus for inductively heating metal workpieces, comprising two spiders; a rotatable shaft on which the said spiders are fixedly mounted; holding centres for workpieces on each of the arms of the said two spiders whereby workpieces may be held between corresponding arms of the said spiders during rotation thereof; means for rotating the said spiders consecutively through predetermined angles whereby workpieces mounted on the arms of the said spiders are moved consecutively into several treating positions, the said means comprising a slot cam fixedly mounted on the said shaft nad cooperating with a roller whereby movement of the roller along a path describing a loop and generated by rotation of a drive shaft having a crank and a rocker linkage, imparts an indexing motion to the spider; the improvement which comprises an automatic control mechanism for lifting,

and lowering an inductor from and to a heating position when a workpiece is indexed to a heating station, said control mechanism comprising a rocking lever adapted and arranged to raise and lower an inductor in response to rocking motions thereof; a heart-shaped disc cam mounted on the aforesaid drive shaft having a crank and rocker linkage; and a follower roller on the said rocking lever cooperating with the said heart-shaped disc cam, whereby the inductor moves to and from a heating position in response to rotation of the said heart-shaped disc cam; and arresting means for preventing movement of the inductor to a heating position in the absence of misalignment of the workpiece in an indexed heating station. I

2. Apparatus as claimed in claim 1, in which the said arresting means comprises a pawl biased by a spring for movement towards an arresting position of the said rocking lever whereby the inductor is held away from a heating position; an electromagnet adapted and arranged to be maintained in an energised state when a workpiece arrives at a heating station in a correctly aligned state and in a nonenergised state when a workpiece fails to reach a heating position in a correctly aligned position; and means for moving the said pawl to a nonarresting position in response to the field generated by the electromagnet.

3. Apparatus as claimed in claim 2, in which the electromagnet is a solenoid, and the said pawl is connected to the moving core of the said solenoid.

4. Apparatus as claimed in claim 2, in which the electromagnet is controlled by control means being a switch or sensor adjacent the heating position of workpieces mounted in the said spider.

References Cited UNITED STATES PATENTS 2,445,822 7/1948 Briechle 2l910.69 2,504,198 4/1950 Jagen 21910.69 X 2,533,919 12/1950 Christiansen et al.

RICHARD M. WOOD, Primary Examiner.

L. H. BENDER, Assistant Examiner.

US. Cl. X.R. 2 l910.7 1 

